Science 609: Energy Transfers and Efficiency | 能量传递与效率

📚 Science 609: Energy Transfers and Efficiency | 能量传递与效率

Energy is everywhere. It moves from one object to another, changes from one form to another, and powers every living and non-living process. In this IGCSE Science revision article, we focus on the key ideas of energy transfer and efficiency that are essential for your Edexcel exams.

能量无处不在。它在物体之间传递，从一种形式转换为另一种形式，并为所有生命和非生命过程提供动力。在这篇IGCSE科学复习文章中，我们集中讲解能量传递与效率的关键概念，这些是Edexcel考试中非常重要的考点。

1. Forms of Energy | 能量的形式

Energy exists in many different forms. The main forms you need to remember are: kinetic (movement), gravitational potential, elastic potential, thermal (heat), chemical, electrical, light, sound, and nuclear.

能量以多种不同形式存在。你需要记住的主要形式包括：动能（运动能）、重力势能、弹性势能、热能（热量）、化学能、电能、光能、声能和核能。

Kinetic energy is any object that is moving.

动能是任何正在运动的物体所具有的能量。
Gravitational potential energy depends on height and mass.

重力势能取决于物体的高度和质量。
Chemical energy is stored in foods, fuels and batteries.

化学能储存在食物、燃料和电池中。

2. The Principle of Conservation of Energy | 能量守恒定律

The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one form to another. The total amount of energy remains constant in an isolated system.

能量守恒定律指出，能量不能被创造或消灭，只能从一种形式转化为另一种形式。在一个孤立系统中，总能量保持不变。

For example, when a ball falls, gravitational potential energy is transferred to kinetic energy. Some energy may also be transferred to thermal energy due to air resistance.

例如，当一个球下落时，重力势能转化为动能。由于空气阻力，部分能量也可能转化为热能。

Total energy before = Total energy after

总能量前后守恒

3. Energy Transfer Diagrams | 能量传递图

Energy transfer diagrams use arrows to show the input energy and what output energies are produced. They are also called energy flow diagrams.

能量传递图使用箭头表示输入的能量以及产生的各种输出能量，这种图也被称为能量流动图。

In a simple circuit, the battery supplies chemical energy, which is transferred to electrical energy in the wire, then into light and thermal energy in the bulb.

在一个简单电路中，电池提供化学能，化学能转化为导线中的电能，然后在电灯泡中转化为光能和热能。

Input energy = the energy supplied to a device.

输入能量 = 供应给设备的能量。
Useful output energy = the energy that a device is designed to produce.

有用输出能量 = 设备设计要产生的能量。
Wasted output energy = energy that is not useful, often thermal energy.

无效输出能量 = 不有用的能量，通常是热能。

4. Calculating Efficiency | 效率计算

Efficiency tells us how good a device is at converting input energy into useful output energy. Efficiency can be written as a decimal, a fraction, or a percentage.

效率表示一个设备将输入能量转化为有用输出能量的能力。效率可以写成小数、分数或百分数。

Efficiency = (Useful output energy ÷ Total input energy)

效率 = （有用输出能量 ÷ 总输入能量）

To express efficiency as a percentage, multiply the value by 100%. For example, if a lamp has 100 J of electrical energy input and 80 J of light output, its efficiency is 80 J ÷ 100 J = 0.8 = 80%.

要得到百分数效率，将数值乘以100%。例如，如果一个灯泡输入100 J电能，输出80 J光能，则其效率为80 J ÷ 100 J = 0.8 = 80%。

5. Sankey Diagrams | 桑基图

A Sankey diagram is a type of energy transfer diagram where the width of each arrow represents the amount of energy. It clearly shows useful and wasted energy.

桑基图是一种能量传递图，图中每个箭头的宽度代表能量的大小。它能够清楚展示有用能量和浪费的能量。

In a Sankey diagram, the input arrow enters from the left. It splits into a horizontal arrow for useful energy and a downward arrow for wasted energy.

在桑基图中，输入箭头从左边进入，然后分支为水平箭头（表示有用能量）和向下箭头（表示浪费能量）。

The thicker the arrow, the greater the energy.

箭头越宽，代表能量越大。
Useful energy is often drawn straight ahead.

有用能量通常画成水平直向。
Wasted energy is often drawn downwards or angled away.

浪费能量通常画成向下或偏转离开。

6. Thermal Energy Transfer | 热能的传递

Thermal energy always transfers from a hotter region to a colder region. It can be transferred by conduction, convection and radiation.

热能总是从较热的区域传递到较冷的区域。热能可以通过传导、对流和辐射三种方式传递。

Heat flows from high temperature to low temperature

热量从高温流向低温

The rate of thermal energy transfer depends on the temperature difference: the larger the temperature difference, the faster the transfer.

热能传递的速率取决于温度差：温度差越大，传递越快。

7. Conduction, Convection and Radiation | 传导、对流与辐射

Conduction is the transfer of thermal energy through a material without the material itself moving. Metals are good conductors; wood and plastic are good insulators.

传导是通过材料本身不移动而传递热能的方式。金属是良好的导体；木头和塑料是良好的绝缘体。

Convection is the transfer of thermal energy by the movement of fluids (liquids and gases). Hot fluid rises, cools, and sinks, creating a convection current.

对流是通过流体（液体和气体）的移动来传递热能。热流体上升，冷却后下沉，形成对流循环。

Radiation transfers thermal energy as electromagnetic waves. It does not need a medium and can travel through a vacuum. Dark, dull surfaces are better emitters and absorbers of radiation than light, shiny surfaces.

辐射以电磁波的形式传递热能，不需要介质，可以在真空中传播。深色、粗糙的表面比浅色、光滑的表面更容易发射和吸收辐射。

8. Energy Resources | 能源资源

Energy resources are sources of energy that humans use. Some are non-renewable, such as coal, oil and natural gas. Others are renewable, such as solar, wind, hydroelectric and geothermal energy.

能源资源是人类使用的能量来源。有些是不可再生能源，如煤、石油和天然气。其他是可再生能源，如太阳能、风能、水能和地热能。

Non-renewable	Renewable
Coal, oil, natural gas	Solar, wind, hydro, tidal, geothermal, biomass
Limited supply	Unlimited supply
Releases CO₂ when burned	Generally low emissions

9. Renewable and Non-renewable Advantages and Disadvantages | 可再生与不可再生能源的优缺点

Fossil fuels are reliable and provide large amounts of energy, but they produce greenhouse gases and contribute to climate change.

化石燃料可靠且能提供大量能量，但会产生温室气体并导致气候变化。

Renewable energy resources generally cause less pollution, but they are often less reliable or have high initial costs. For example, solar power does not work at night, and wind power depends on the weather.

可再生能源通常污染较少，但往往不太可靠或初始成本较高。例如，太阳能发电在夜间无法工作，风能取决于天气。

Coal: cheap and abundant, but high pollution.

煤：便宜且储量丰富，但污染严重。
Solar: clean and free, but intermittent.

太阳能：清洁且免费，但间歇性供应。
Wind: clean, but noisy and land-intensive.

风能：清洁，但有噪音且占地多。

10. Reducing Energy Losses | 减少能量损耗

In houses and machines, energy can be lost as heat. We can reduce energy losses using insulation, lubrication and more efficient designs.

在房屋和机器中，能量可能以热的形式损失。我们可以通过保温、润滑和更高效的设计来减少能量损失。

For example, cavity wall insulation reduces heat loss by conduction and convection in walls. A radiator reflector reflects heat back into the room instead of allowing it to escape through the wall.

例如，空心墙保温层可以减少墙壁中通过传导和对流造成的热量损失。散热器反射板可将热量反射回房间，而不是让它通过墙壁逸散。

Energy efficiency = 100% − energy lost as heat

能量效率 = 100% − 以热形式损失的能量

Lubricating moving parts reduces friction, which converts kinetic energy into unwanted thermal energy.

润滑运动部件可以减少摩擦，因为摩擦会把动能转化为不需要的热能。

11. Efficiency in Food Chains | 食物链中的效率

Energy also transfers through ecosystems. Plants convert light energy into chemical energy by photosynthesis. When animals eat plants, only about 10% of the energy passes to the next trophic level.

能量也在生态系统中传递。植物通过光合作用将光能转化为化学能。当动物吃植物时，只有大约10%的能量传递到下一营养级。

Most energy is lost through respiration, movement, growth and waste products.

大部分能量通过呼吸作用、运动、生长和排泄物损失。

Producers: make their own food using light.

生产者：利用光制造自身食物。
Consumers: obtain energy by eating other organisms.

消费者：通过吃其他生物获取能量。
Decomposers: break down dead organisms, returning nutrients to the soil.

分解者：分解死亡生物体，将养分归还土壤。

12. Summary | 总结

Energy cannot be created or destroyed. Efficiency measures how much useful energy is obtained from an input. Reducing energy loss is important for saving resources and cutting pollution.

能量不能被创造或消灭。效率衡量从输入中获得多少有用能量。减少能量损失对于节约资源和减少污染非常重要。

Always remember the efficiency formula and be able to draw or interpret energy transfer diagrams. These skills appear frequently in Edexcel IGCSE Science questions.

务必记住效率公式，并能够绘制或解读能量传递图。这些技能在Edexcel IGCSE科学试题中经常出现。

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Science 609: Energy Transfers and Efficiency | 能量传递与效率